Double asteroid belt in

Solar System clone
BY DR EMILY BALDWIN
ASTRONOMY NOW

Posted: October 27, 2008

Spitzer observations have discerned two rocky asteroid belts and an icy outer ring surrounding our Sun’s doppelgänger Epsilon Eridani that could have been shaped by evolving planets.

"This system probably looks a lot like ours did when life first took root on Earth," says lead author of the study Dana Backman of the SETI Institute.

Click to enlarge. Our familiar Solar System compared with the similar layout of Epsilon Eridani's system. Both systems host asteroids (brown), comets (blue) and planets (white dots). Image: NASA/JPL-Caltech.

Epsilon Eridani, visible to the naked eye and located just 10.5 light years away in the constellation Eridanus, is marginally smaller and cooler than our own Sun, but at just 850 million years old is providing insight into how our Solar System evolved. It already shares striking similarities to the formation we are familiar with today, bearing an inner rocky asteroid belt at an equivalent distance from the central sun as our own inner Astroid Belt. An outer rocky belt containing around 20 times as much material also exists in the same position as Uranus.

A third ring of icy material spans a ring from 35 to 100 AU, mimicking the Kuiper belt of our own Solar System but with 100 times more material. But when our own Sun was a spritely 850 million years old, our icy reservoir probably looked much the same as Epsilon Eridani’s, prior to a dramatic clearing out of rocky material during the Heavy Bombardment Era, where material was flung into the inner planets and some even hurled out of the Solar System altogether.

"Epsilon Eridani looks a lot like the young Solar System, so it's
conceivable that it will evolve similarly," says Massimo Marengo of the Harvard-Smithsonian Center for Astrophysics.

Artist impression of the Epsilon Eridani solar system, exhibiting a double asteroid belt and a reservoir of icy cometary material. Image: NASA/JPL-Caltech.

The forming solar system was observed by the Spitzer Space Telescope, and revealed gaps between each of the rings orbiting the central star. Such gaps are best explained by the presence of planets that gravitationally mold the rings and sweep out material as they orbit their central star.

"Planets are the easiest way to explain what we're seeing," says Marengo. Indeed, the astronomers predict that three planets with masses between those of Neptune and Jupiter must be lurking in the system, and a candidate planet near the innermost ring already has been detected by radial velocity studies. A second planet is inferred near the outer asteroid belt at a distance of 20 AU, and a third at about 35 AU near the inner edge of the Kuiper Belt clone.

There is no doubt that the Epsilon Eridani system will be the first on many a planet hunter’s list, and as the resolving power of telescopes increases, astronomers hope to detect terrestrial and even Earth-mass planets orbiting inside the innermost asteroid belt for a true Solar System analogue.

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